smb2_server: use MSG_DONTWAIT to get non-blocking send/recvmsg

It means we can make the fd blocking, which will help
with io_uring support.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

diff --git a/source3/smbd/smb2_server.c b/source3/smbd/smb2_server.c
index d768c0b0f8437756adae33e94def596373c8949f..462e0d7ecacadfe1bb5768f0bf4d63192929312f 100644 (file)
--- a/source3/smbd/smb2_server.c
+++ b/source3/smbd/smb2_server.c
@@ -324,11 +324,23 @@ static NTSTATUS smbd_initialize_smb2(struct smbXsrv_connection *xconn,
        }
        tevent_fd_set_auto_close(xconn->transport.fde);
 
-       /* Ensure child is set to non-blocking mode */
+       /*
+        * Ensure child is set to non-blocking mode,
+        * unless the system supports MSG_DONTWAIT,
+        * if MSG_DONTWAIT is available we should force
+        * blocking mode.
+        */
+#ifdef MSG_DONTWAIT
+       rc = set_blocking(xconn->transport.sock, true);
+       if (rc < 0) {
+               return NT_STATUS_INTERNAL_ERROR;
+       }
+#else
        rc = set_blocking(xconn->transport.sock, false);
        if (rc < 0) {
                return NT_STATUS_INTERNAL_ERROR;
        }
+#endif
 
        return NT_STATUS_OK;
 }
@@ -4728,6 +4740,7 @@ static NTSTATUS smbd_smb2_flush_send_queue(struct smbXsrv_connection *xconn)
 
        while (xconn->smb2.send_queue != NULL) {
                struct smbd_smb2_send_queue *e = xconn->smb2.send_queue;
+               unsigned sendmsg_flags = 0;
                bool ok;
                struct msghdr msg;
 
@@ -4801,7 +4814,14 @@ static NTSTATUS smbd_smb2_flush_send_queue(struct smbXsrv_connection *xconn)
                        .msg_iovlen = e->count,
                };
 
-               ret = sendmsg(xconn->transport.sock, &msg, 0);
+#ifdef MSG_NOSIGNAL
+               sendmsg_flags |= MSG_NOSIGNAL;
+#endif
+#ifdef MSG_DONTWAIT
+               sendmsg_flags |= MSG_DONTWAIT;
+#endif
+
+               ret = sendmsg(xconn->transport.sock, &msg, sendmsg_flags);
                if (ret == 0) {
                        /* propagate end of file */
                        return NT_STATUS_INTERNAL_ERROR;
@@ -4864,6 +4884,7 @@ static NTSTATUS smbd_smb2_io_handler(struct smbXsrv_connection *xconn,
        struct smbd_smb2_request_read_state *state = &xconn->smb2.request_read_state;
        struct smbd_smb2_request *req = NULL;
        size_t min_recvfile_size = UINT32_MAX;
+       unsigned recvmsg_flags = 0;
        int ret;
        int err;
        bool retry;
@@ -4909,7 +4930,14 @@ again:
                .msg_iovlen = 1,
        };
 
-       ret = recvmsg(xconn->transport.sock, &msg, 0);
+#ifdef MSG_NOSIGNAL
+       recvmsg_flags |= MSG_NOSIGNAL;
+#endif
+#ifdef MSG_DONTWAIT
+       recvmsg_flags |= MSG_DONTWAIT;
+#endif
+
+       ret = recvmsg(xconn->transport.sock, &msg, recvmsg_flags);
        if (ret == 0) {
                /* propagate end of file */
                status = NT_STATUS_END_OF_FILE;